Temperature responsive device



Oct. 8, 1940. w. A. BARNES 2,217,328

TEMPERATURE RESPONSIVE DEVICE Filed Jan. 51, 1938 Campen Smsp SAMELENQTH As Owml.. Houza 1 2 Campen STfzrpToo 5m; INVENTOR.

v vPatented Oct. 8, i940',

UNITED STATES PAT-ENT OFFICE- TEMPERATURE RESPONSIVE DEVICE William A. Barnes, Manliield, Ohio,l alaiguor to Dominion Electrical Manufacturing Company Application January 3l, 1938, Serial No. 187.883 I 20Claima.

My invention relates in general to temperature responsive devices, and more particularly to temperature responsive devices arranged to control electrical appliances.

An' object of my invention is the provision of av temperature responsive device having metallic elements in which one of the metallic elements comprises an aluminum strip.

Another object of my invention is to provide for opposing the permanent growth of an aluminum element utilized in the construction of a temperature responsive device. I

Another object of my invention is to provide for utilizing in a temperature responsive device a reative thin longitudinal aluminum member shaped to have a relatively high section modulus to oppose any bending action therein incident to contraction and expansion.

Another object of my invention is to provide for utilizing in the construction of a temperature responsive device a longitudinal aluminum channel member having a relatively high section modulus to oppose any bending action therein incident to contraction and expansion.

Another object of my invention is to provide for compressing an aluminum element of a temperature responsive device lengthwise to oppose the permanent growth of the aluminum element.

Another object of my invention is the provision of a temperature responsive device comprising metallic longitudinal elements joined at their ends and arranged to have different section moduli, so that substantially al1 of the movement due to the contraction and expansion of 'the elements occurs in one of the elements only.

Another object oi my invention is to provide for causing the moving element of a temperature responsive device to have the rigid eilect of a short strip but the expansion eiect of a long strip.

Another object of my invention is the provision of a crimped element in a temperature responsive device to give the effect of a rigid short strip but the expansion eii'ect of a long strip.

Another object of my invention is to provide in a temperature responsive device for foreshortening a crimped longitudinal metallic strip so that when it is joined with the ends of an aluminum strip it causes the aluminum strip to be compressed lengthwise to oppose the permanent growth of the aluminum strip.

f Another object of my invention is the provision of utilizing an aluminum strip in the construction of a temperature responsive device, so that the aluminum strip will maintain its origi- (Cl. 20o-137) nalcharacteristics throughout a period o! relatively long use.

Another object of my invention is the Provision of a temperature responsive device employing an aluminum element as one of the metallic elements, in which the adjustable setting of temperature responsive device remains substantially the same throughout a long period of use.

Another object of my invention is the provision of utilizing my temperature responsive device 10 in electrical household appliances.

Other objects and a fuller understanding of my invention may be had by referring to the following description and claims, taken in conjunctionv with the accompanying drawing, in which like l5 parts are designated by like reference characters. and in which:

Figure 1 illustrates my temperature responsive device mounted upon the heating plate oi' an electrical appliance, such for example, as a wallie 20 iron plate;

Figure 2 designates a cross-sectional view of Figure 1, taken along the line 2 2 of Figure 1;

Figure 3 shows a plan view of the metallic longitudinal elements of my temperature responsive 25 device;

Figure 4 shows a side view of the longitudinal metallic elements of my temperature responsive device, with the channel member shown in crosssection and with the upper longitudinal crimped 30 strip shown as being foreshortened preparatory to joining the two metallic elements together;

Figure 5 is the cross-sectional view taken along the line 5-5of Figure 1;

Figure 6 shows a diagrammatical illustration of the permanent growth of an aluminum strip when employed as an element of a temperature responsive device, with the crimped strip the same length as the aluminum channel;

Figure 7 shows a diagrammatical illustration o of the permanent growth of an aluminum strip when employed as an element in a temperature responsive device, with the crimped strip too short;

Figure 8 shows a graph illustrating the eect u of the permanent growth of an aluminum strip when used as a metallic element of a temperature responsive device.

With reference to the drawing, my temperature responsive device is indicated generally by the reference character 20, and in Figures 1 and 2, it is shown as being mounted upon a waiile iron plate 2|, heated by a heating element 22 energized by the supply conductors 23 and 2l which are respectively connected to the terminals .5 :5

extending notches into which the heating element 22 may be positioned. The insulated supports 3| and 32, and 34 and 35 may be held in position by means of metal brackets 36 and 31, respectively, which may be fastened to the waflle iron plate 2| by means of the screw 38 and 39. 'I'he insulated support 33 may be held in position .by means of a metal bracket 40 which is suitably fastened to the right hand end of my temperature responsive device 20 by the rivets 4|.

The metallic elements of my temperature responsive device comprise a longitudinal channel member 45 and a longitudinal crimped strip 46 having their ends joined by means of the rivets 4| and 58. In the embodiment of my invention, I preferably construct the channel member 45 of aluminum which has a relatively high coefcient of expansion and the longitudinal crimped strip 45 is preferably constructed of a piece of stainless steel which has a relatively low coefcient ci expansion. As illustrated, the central portion of the longitudinal crimped strip 46 is provided with an insulated actuating member 56 arranged to actuate the contact member 48 relative to the contact member 4l which are carried on the right hand end of the resilient contact fingers 5'. and 5E, respectively. The left hand end of the resilient contact fingers 51 and 58 are mounted to a supporting plate 49 by means or insulating washers 59 and 6G which are held in position by the nut and holt assembly 6| and 62. The nuts or the bolts are likewise insulated from the supporting plate 49 by means of insulating members 33 which are positioned between the nuts and the heads of the screws and the supporting plate 49. Any suitable means may be employed to secure the supporting plate 48 to the top edges o1 the channel member 4G, and as il1ustrated, l employ four talos S6 along the upper edge of the insidesI of channel member 46. The tabs 83 extend through registered openings of the supporting plate 4t and are upset to form a rivet like construction. The entire assembly of my temperature responsive device 20 may be held in fixed engagement with the Waiiie iron plate 2| by means of studs 51 and 69 having their lower ends threadably secured in the wallie iron plate 22 and having their upper ends provided with nuts 68 and 10 which screw down on top of the supporting plate 49.

The Contact member 41 is arranged to be adjustably positioned with reference to the contact member 48 by means of an adiustable screw 1| threadably mounted in a collar 14 mounted on top of the supporting plate 49, The lower end of the adjustment screw 1| is recessed and provided with an insulating member 12 which directly engages the resilient contact linger 58. The adjustment screw 1| may be adjustably turned in any suitable manner and as illustrated I employ a lever 13 which may be actuated by the user to regulate the temperature of the electrical appliance.

The energization of the heating element 22 is controlled by the contacts 41 and 48 governed by the contraction and expansion of the channel member 45 and the stainless steel strip-46, When the temperature of the waiiie iron plate 2| exceeds a predetermined value, as determined by the setting of the adjustment screw 1|, the aluminum channel member 45 expands and draws the central portion of the stainless steel strip 46 downwardly and thereby permits the contact 48 to separate from the contact 41 to de-energize the heating element 22. When the temperature of the wallie iron plate 2| recedes to a predetermined low value, the aluminum channel member 45 contracts and forces the central portion of the stainless steel strip upwardly and causes the contact 48 to engage the contact 41 which closes the circuit for energizing the heating element 22. When the circuit is closed, the flow of the current may be traced from the supply conductor 23 through the terminal 25, the heating element 22, the terminal 26, the resilient contact finger 51, the contacts 41 and 48, the resilient contact finger 58, the terminal 21 to the other supply conductor 24.

Aluminum is an excellent metal to be employed in a temperature responsive device because of its relatively high coeilicient of expansion but because of its permanent growth characteristic, it has never been commercially feasible for use in electrical appliances in relatively thin strips. Also, heretofore, it has never been commercially possible to employ a relatively thin aluminum strip as an element of a temperature responsive device in which the appliance exceeded a temperature in the neighborhood of 300 degrees F. This is because the aluminum strip would loose its original characteristics and the setting of the temperature responsive device would be thereby proportionately disturbed. For example, the temperature responsive device may be adjustably set to give a temperature of 500 degrees F. for baking wailles and after continued use of alternate expansions and contractions of the aluminum strip, the temperature setting may drop as low as 425 degrees F. resulting from the permanent growth of the aluminum. A drop in temperature to or below 425 degrees F. is inadequate to bal-:e Waies satisfactorily. In an iron, if the temperature drops much below the neighborhood of 450 degrees F., it becomes undesirable for general use. In a sandwich toaster, if the temperature drops much below 375 degrees F., it will not toast the sandwich. In order to overcome the permanent growth which disturbs the setting of the temperature of the appliance, I provide for compressing the aluminum strip lengthwise to oppose the permanent growth and thereby enable an aluminum strip, which heretofore was undesirable for high temperatures, to be used at high temperatures such as employed in wallie irons, sandwich toasters and electric irons. I arrange to compress the aluminum channel member 45 lengthwise by foreshortening the crimped strip 46, as illustrated in Figure 4, by the offset center lines passing through the rivet openings in the ends of the channel member 45 and the longitudinal strip 46. The aluminum channel member 45 and the stainless steel strip 46 shown in Figures l, 2, 3, 4, and 8 are drawn to scale of an'actual embodiment of my invention and the registered openings at the ends of the channel member 45 and the stainless steel strip 45 for the rivets 4| and 50 are such that the openings in the stainless steel strip 46 are foreshortened approximately fifteen thousandths of an inch preparatory to joining the two members together. In joining the two members together by means of the rivets 4| and 50, the stainless steel strip 46 is pressed downwardly at its central portion to elongate the same to make the openaluminum channel 45, as will occur through ordinary and continued use. In the embodiment ofV my invention, the alumnium strip is in the form of a channel member to give a relatively high section modulus to oppose any bending action therein incident to contraction and expansion. The channel construction also makes it possible to reduce the mass of the aluminum member so that it is immediately responsive to changes in temperatures. The channel construction in addition, shields the stainless steel strip 46 from being directly influenced by the heating element 22 of the wallie iron or any other heating element which may be used in electrical appliances.

In order to give the rigid eiect of a short strip but the expansion eect of a long strip, I provide for crimping the longitudinal strip 45, producing crimped peak portions I, 52, and '53, and crimped depressed portions 54 and 55, the latter of which engage the bottom of a channel member 45 to give rigidity to the intermediate portion of the strip 45 which lifts the resilient contact finger 5l. Therefore, the distance between the depressed crimp portions 54 and 55 is substantially one-half the overall length of the strip member 45. This reduction in length more than doubles the rigidity for lifting purposes, but retains the expansion effect of the entire length of the strip.

In Figure 6, I show diagrammatically the eilect of the permanent growth of the aluminum channel member 45 when the registered openings through which the rivets 4l and 50 pass, prior to assembly.v are the same length for both the crimped strip 46 and the channel member 45. If the temperature responsive device is set originally at 500 degrees F., the elongation of the aluminum channel member 45 resulting from the permanent growth may cause the setting of the temperature responsive device to drop to a temperature as low as 450 degrees F. after a short period of use. Continued use may cause the setting to drop as low as 430 degrees F., as diagrammatically illustrated in Figure 6. This dropping characteristic is further illustrated in the graph in Figure 8, in which the dot-and-dash line 'l5 represents the drop in temperature after each hourly interval of alternate heating and cooling of the appliance. In Figure 8, beginning at the left-hand side of, the graph, the temperature responsive device is adjustably set at 500 degrees F. At the end of one hour, the appliance is disconnected and allowed to cool for an hour. At the beginning of the second hour, the appliance is again connected and the temperature of the appliance rises but does not attain 500 degrees F.,v but falls slightly below as illustrated. At the end of the third hour, the appliance is again turned oil and allowed to cool for an hour, at which time the appliance is again energized and the temperature to which it attains is slightly decreased a further amount. The alternate periods of heating and cooling continues and upon each alternate period, the temperatures fail to reach a value equal to its next preceding temperature.

In Figure 7, I show a diagrammatic arrangement where the stainless steel strip 46 is too short and the aluminum is compressed too much. In a construction of this kind. the setting of the temperature rises upon each alternate heating and cooling. Thus, the original temperature may be adiustably set for 500 degrees F. which may' gradually rise as high as 550 degrees F. after a short period of use. Continued use may cause the temperature to reach 570 degrees F. The increasing temperature characteristics in Figure 7, caused by too much compression, is shown in Figure 8 by the dotted line 16 which shows that upon each alternate cooling and heating the temperature gradually rises. The full line 11 shows the characteristics of my temperature responsive device where the aluminum channel is compressed the exact amount to oppose equally the permanent growth of the aluminum incident to expansions and contractions. Therefore by means of my construction, I have made it possible to employ an aluminum strip as one of the metallic elements of a temperature responsive device suitable. for commercial employment in electrical devices having temperatures considerably higher than that in which an alution and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim as my invention:

1. Means for preventing creep in a tempera-v ture responsive device comprising, in combination, longitudinal metallic elements having their ends secured together and having different coeilicients of expansion, the element having the lower coefficient of expansion comprising a longitudinal strip having a portion intermediate'its ends arranged to move respectively away from or toward the element having the higher coefficient of expansion upon the contraction or expansion of the said element having lthe higher coeilicient of expansion, the element having the higher coeicient of expansion comprising a thin longitudinal aluminum member subject to creep and shaped to have a relatively high section modulus to oppose any bending action therein incident to the contraction and expansion of the elements, the element having the lower coeilicient of expansion compressing the aluminum member lengthwise throughout the temperature range of the device and at all times to substantially prevent the permanent growth.

2. A temperature responsive device comprising, in combination, longitudinal metallic elements having their ends secured together and having diierent coelllcients of expansion, the element having the lower coetlicient of expansion comprising a longitudinal strip having a portion intermediate its ends arranged to move respectively away from or toward the element having the higher coecient of expansion upon the contraction or expansion of the said element having the higher coelcient of expansion, the element having the lower coeicient of expansion also l having the lower coefllcient of expansion comprising a longitudinal strip having a portion intermediate its ends arranged to move respectively away from or toward the element having the higher coemcient oi expansion upon the contraction or expansion of the said element having the higher coefllcient of expansion, the element having the lower coefllcient of expansion also having two spaced portions located inwardly oi the ends thereof for engaging the other metallic element to give the rigid effect oi a short strip but the expansion eifect of a long strip.

4. A temperature responsive device comprising, in combination, longitudinal metallic elements having their ends secured together and having different coeiiicients of expansion, the element having the lower coeiiicient of expansion cornprising a longitudinal strip crimped intermediate its joined ends and engaging the other metallic element at the crimped places to give the rigid effect of a short strip but the expansion eiect of a long strip.

5. A temperature responsive device comprising, in combination, longitudinal metallic elements having their ends secured together and having diiferent coefficients of expansion, the element having the higher coeiiicient of expansion comprising an aluminum channel member, the element having the lower coeflicient of expansion comprising a longitudinal strip crimped intermediate its joined ends and engaging the aluminum channel member at the crimped places to give the rigid effect of a short strip but the expansion effect of a long strip, said crimped longitudinal strip being foreshortened to compress i the aluminum channel member lengthwise to oppose the permanent growth thereof.

6. A temperature responsive device comprising, in combination, longitudinal metallic eleuments having their ends secured together and having different coefiicients of expansion, one

of said elements being bent intermediate its ends and engaging at said bent place said other element which has a permanent growth characteristic, said crimped element being foreshortened to compress said other element lengthwise to oppose the permanent growth thereof.

7. Means for preventing creep in a temperature responsive device comprising, in combination, longitudinal metallic elements having their ends secured together and having diiierent coefcients of expansion, one of said elements being aluminium subject to permanent growth and the other element being foreshortened to compress the aluminium element throughout the temperature range of 'the device to prevent the permanent growth thereof.

8. A temperature responsive device comprising, in combination, longitudinal metallic elements having their ends secured together and having dierent coefficients of expansion, one of said elements being bent intermediate its ends to engage the other to give the rigid effect of a short strip but the expansion effect of a long strip.

9. A temperature responsive device comprising, in combination, longitudinal metallic elements having their ends secured together and having different coeiiicients of expansion, one of said elements having two longitudinal portions, one of said longitudinal portions being spaced from said other element to provide means for actuating said temperature responsive device and the other of said longitudinal portions being arranged to engage said other element along part of its length to give the rigid effect oi a short strip but the expansion eiIect o! a long strip.

10. Means for preventing creep in. a temperature responsive device comprising, in combination, longitudinal metallic elements having their ends secured together and having different coemclents of expansion, the element having the higher coemcient of expansion comprising an aluminum channel member with a creep characteristic, said other element having a tensile stress which is opposed by a lengthwise compressive stress in said aluminum channel member throughout the temperature range oi the device, said lengthwise compressive stress'substantially eliminating said creep characteristic.

ll. Means for preventing creep in a temperature responsive device comprising, ln combination, longitudinal metallic elements having their ends secured together and having different coefilcients of expansion, the element having the higher coeiiicient of expansion comprising an aluminum member with angularly disposed portions and with a creep characteristic, said other element having a tensile stress which is opposed by a lengthwise compressive stress in said aluminum member throughout the temperature rangeof the device, said lengthwise compressive stress substantially eliminating said creep characteristic.

l2. Means for preventing creep in a temperav ture responsive device comprising longitudinal metallic elements having their ends secured together and having different coeii'icients of expansion, the rst of said elements being subject to creep and the second of said elements having a stress therein which stresses said first element throughout the temperature range of the device to substantially prevent the creep thereof.

l3. Means for preventing creep in a temperature responsive device comprising, longitudinal' metallic elements having their ends secured together and having substantially equal and opposite forces therein, one of said longitudinal elements being subject to creep, and opposing force in said other element acting upon said element subject to creep to prevent the creep substantially throughout the temperature range of the device.

14. In a temperature responsive device, a longitudinal metallic element subject to creep due to repeated temperature changes, and means comprising a second metallic element for putting a compressive stress into said longitudinal metallic element to substantially prevent said creep throughout the temperature range of the device.

i5. In a temperature responsive device, an element subject to creep due to repeated changes in temperature and resilient means engaging said element for putting a balancing force on said element throughout the i of temperature Change of said device. said balancing force being substantially equal :lo and opposite a force established by said creep tendency' thereby substantially preventing said creep.

i6. A temperature responsive device for electrical apparatus comprising, in combination, longitudinal metallic elements having their ends secured together and having different coeiilcients of expansion, the element having the higher coeicient of expansion comprising an elongated aluminum channel member having a bottom and sides with an open top, a top member attached to said sides, insulating means attached to said top member, a pair of contacts mounted on said insulating means and positioned within said channel member, said longitudinal metallic elements upon a change in temperature actuating one of said contacts with respect to the other to automatically regulate the electrical circuit through the said-apparatus.

17. A temperature responsive device for electrical apparatus comprising, in combination, longitudinal metallic elements having their ends secured together and having different coeiiicients of expansion, the element having the higher coeilicient of expansion comprising an elongated aluminum channel member having a bottom and sides with an open top, the said sides of the channel member having tabs thereon, a top member with holes therein, said tabs itting in the said holes in the said top member and attaching said top member to the said sides, insulating means attached to said `top member, a pair oi' contacts mounted on said insulating means and positioned within said channel member, said longitudinal metallic elements upon a change in temperature actuating one of said contacts with respect to the other to automatically regulate the electrical circuit through the said apparatus.

18. A temperature responsive device i'or electrical apparatus comprising, in combination, longitudinal metallic elements having their ends secured together and having diiierent coefllcients of expansion, the element having the higher coefficient of expansion comprising an elongated aluminum channel member having a bottom and sides with an open top, a top member attached to said sides, insulating means attached to said top member, a pair oi' contacts mounted on said insulating means and positioned within said channel member, said longitudinal metallic elements upon a change in temperature actuating one of said contacts to automatically regulate the electrical circuit through the said apparatus. and

manually operable means mounted on said top member for actuating the other of said contacts to regulate the electrical circuit through the said apparatus.

19. In a thermostatic switch having a pair of contacts to regulate the ilow of electric current through an electrical apparatus, in combination, longitudinal metallic elements having their ends secured together and having different coeilicients of expansion, the element having the higher coefncient of expansion comprising an elongated aluminum channel member having a bottom and sides with an open top, a top member attached to said sides for supporting said contacts within said channel member, said longitudinal metallic elements upon a change in temperature actuating one of said contacts with respect to the other to automatically regulate the electrical circuit through the said apparatus.

20. In a thermostatic switch having a pair of contacts to regulate the ilow of electric current through an electrical apparatus, in combination, longitudinal metallic elements having their ends secured together and having dierent coeflicients of expansion, the element having the higher coeicient of expansion comprising an elongated aluminum channel member having a bottom and sides with an open top, a top member attached to said sides for supporting said contacts within said channel member, said longitudinal metallic elements upon a change in temperature actuating one of said contacts to automatically regulate the electrical circuit through the said apparatus, and manually operable means mounted .on said top member for actuating the other of said contacts to regulate the electrical circuit through the said apparatus.

WILLIAM A. BARNES. 

